MIS-BGA packaging architecture may be attractive for two factors. First, MIS-BGA architecture may have a relatively low profile (otherwise referred to as “z-height”). Additionally, MIS-BGA architecture may be a relatively low cost architecture as compared to architectures that use Prepreg or Ajinomoto Build-up Film (ABF) because MIS-BGA architecture may not require laser drilling and may use a low cost mold compound rather than the Prepreg or ABF materials.
In some legacy MIS-BGA packages, the process of manufacturing the MIS-BGA package may have included depositing a dry film resist (DFR) to serve as a mask, forming traces and/or pads on a substrate, and then removing the DFR. Subsequently, the process may have included at least partially covering the traces and/or pads with a second layer of dry film resist (DFR), for example, through lamination or some other process. A via may have then been litho-defined through the DFR to the pad to at least partially expose the pad, and then copper may have been plated in the opening to form a plated copper via. Subsequent to this plating, the DFR may have been stripped and a mold compound may have been formed on the pads, traces, and copper via, which would then have to be ground and/or treated so that the surface of the mold was flush with the surface of the via for the subsequent layer formation.
While this technique may offer some cost advantages over ABF-based high density interconnection (HDI) substrate processing, the above described process may use two litho-defined steps, one to create an underlying pad and the 2nd to create the via metal. Further, this process may limit the ability to create fine line and spacing (FLS) of copper traces, especially in all layers of the package. For example, it may be difficult to mass produce traces with a width of less than 15 microns and/or that are spaced less than 15 microns apart from one another (referred to herein as 15/15 L/S), since grinding of dielectric material of the package may be necessary to expose an embedded via inside of a mold compound of the package. Additionally, the above described grinding or surface treatment process may negatively impact reliability or structural stability of the MIS-BGA package.